This series was first published in 1902-06 by Unwin and later reprinted by Cambridge University Press in 1956-1959. Some of these PDFs were scanned by archive.org in 2011, where they can be downloaded in other formats (see archive); others were scanned by Duane Troxel in the 1990s. The text versions below are not edited or proofread; they are simply text extracted from the PDFs.

For the Babi/Bahá'í period, see Volume 4.